Technical Abstract:
Soil quality assessment is a proactive process for understanding the long-term effects of soil and crop management practices within agricultural watersheds. The objective of this study was to assess the impact of management on the soil quality in fields where the management history is known for close to six decades. The fields were located near Riesel TX on the Houston Black soil series (Udic Haplustert), which has a high content of montmorillonitic clay. We sampled five sites representing an untilled native pasture, two previously tilled for row crops and then seeded to coastal Bermuda grass (Cynodon dactylon (L.) Pers.) 57 and 31 years ago, and two fields that have been continuously cropped for most of the last 57 years. Six to eight surface (0 to 10 cm) soil samples were taken from each field. Soil bulk density (BD), aggregate stability (AGG), texture, water-filled pore space (WFPS), pH, Mehlich III extractable P, K, Ca and Mg, KCl extractable NO3 and NH4, DTPA extractable Cu, Fe, Mn and Zn, electrical conductivity (EC), total soil organic carbon (SOC), total N, microbial biomass C (MBC), potentially mineralizable C (Cmin) and N (Nmin) were quantified. In addition four enzyme activities were measured: 1,4 ß- glucosidase (BG, a type of cellulase), N-acetyl ß-D- glucosaminidase (a type of chitinase), acid phosphatase, arylamidase and fluorescein diacetate hydrolysis. The soil quality assessment was conducted using the Soil Management Assessment Framework (SMAF). SMAF indicator score values were calculated for BD, AGG, WFPS, pH, EC, SOC, P, K, MBC, Cmin, Nmin, and BG. Results will be discussed.